Does size matter?: EVs, batteries, and electric miles

With U.S. and California plug-in electric vehicle (PEV) commercialization
underway, the state continues to forge a path forward, incentivizing increasing
numbers of PEVs, more all-electric vehicles, and big batteries. As sales
increase and serious incentive and other investments are being made, examining supportive
policies for their effectiveness over time is increasingly important. This blog
provides some background for that effort by: discussing the state’s
zero-emission-vehicle (ZEV) policy, introducing the importance of electric
miles (e-miles) as a metric linking ZEVs to their impact, and examining the
e-mile potential and cost-effectiveness of the current fleet of light-duty PEVs
in the U.S.

3.3 is better than 1.5

Yesterday, the California Air Resources Board (CARB) held a
hearing to review the latest proposed changes to its landmark regulations for
zero-tailpipe-emission vehicles (ZEVs) and to get an update on the extension of
that program through 2025 under the auspices of the Advanced
Clean Cars program.

As part of an event concerned with changes that can fairly
be considered minor relative to a history of major overhauls starting back
in 1996, there nevertheless was a significant announcement: the unveiling of a memorandum of
understanding signed by 8 out of the 9 governors of states in the union that
have chosen to adopt California’s more aggressive vehicle regulations rather
than stay on cruise control with the federal standards. Joining forces in this
public way, CARB was able to riff on the meme created by the Governor Brown’s
Executive Order calling for 1.5 million ZEVs on California roads by 2025 with a
CARB homepage headline that reads: “3.3
Million Zero Emission Vehicles by 2025.”

But it is complicated

Under the surface, the hearing, and the ZEV regulations,
create a much more complicated picture. This is due to a complex and evolving
ZEV credit scheme that disconnects the number of credits from the number of
vehicles. It was originally phrased as a percentage, e.g., 2% of all vehicles produced
for sale in California in 1998 shall be ZEVs. It was adapted into a flexible
credit banking and trading system that has allowed partial credit for vehicles with
combustion engines and has given extra credit for desired vehicle attributes—e.g.,
long electric range provided by big batteries. It also requires increasing
numbers of all-electric vehicles over time. Plug-in hybrids—which can in
practice be ZEVs but can also operate having never seen a charge station—are
allowed to contribute, but for less credit per vehicle and in a diminishing
second class referred to as “transitional.”

Through this complex ZEV credit system—along with a host of
related and supportive other policies such as differential purchase rebates and
carpool lane stickers, and investments in infrastructure implicitly or
explicitly supportive of specific kinds of PEVs and drivers—California effectively
incentivizes a complex, confounded web of factors relating to PEVs and electric
fuel. Many of these factors—e.g., battery size and number of all-electric
vehicles—are good factors to increase over time, and there are a wider variety
of justifications for doing so than will be articulated here. However, many of
these factors are rough proxies for the real headline, which isn’t the number
of cars or even reduced emissions, but avoided damage to human and natural
systems. But these factors are separated from impact by several links in a
complex chain of causality that introduces uncertainty at each stage (Figure
1).

Figure 1. Complex
casual chain of compounding uncertainty

Stepping forward: e-miles

To examine the effectiveness of policies supportive of PEVs
and electric fuel, it is therefore desirable, when practical, to understand links
in the chain leading to impact. An important linkage between ZEVs and their
impact is, in a word, “use.” Producing high volumes of big-batteried vehicles
for sale could be important (e.g., for reaching critical economies
of scale in vehicle and battery-cell production [1]). But it only gets us partway
to reduced impact if those vehicles aren’t out on the roads displacing many petroleum-fuel
vehicle miles travelled (VMT) with those fueled by electricity (e-VMT). And
thus, increasing attention is being paid not just to the size of batteries and
the number of vehicles, but to “e-miles.”

Chopping things down to size

Even without data directly measuring e-VMT accumulation by
the U.S. fleet, an interesting picture emerges when we consider both market
adoption and expected use. Figure 2 illustrates the total e-mile potential of
PEVs sold
in the U.S. from December 2010 through September 2013 [2]. The first column is the sum
of the sales-weighted electric ranges of the U.S. PEV fleet. In essence, it
shows how many e-miles U.S. PEVs could
provide with each charge. The second column caps the e-range of each
vehicle at 30 miles per day, a reasonable estimate of average daily driving. In
essence, it shows how many e-miles U.S. PEVs are likely to provide each day (e.g., assuming that each vehicle
returns home each night to recharge).

Figure 2.

As can be seen in the figure, the e-mile potential of the
U.S. fleet decreases dramatically for the expected-use case. Further, the vast
majority of that decrease comes from all-battery electric vehicles (BEVs).
Indeed, on a sales-weighted basis in expected use, plug-in-hybrid EVs (PHEVs)
actually contribute more daily e-mile
potential, in total. Thus, at this particular moment in time, the
“transitional,” less incentivized class of plug-in hybrids with relatively
small batteries is probably doing more than their share of cleaning the air.

Figure 3 illustrates this fact further by showing how many
daily miles of travel would be required, on average, of the existing fleet of
PEVs for the contribution to be equal: 36 miles per day—a significant increase.
Indications are that this comparison may be conservative—at the CARB hearing it
was mentioned that data from the EV Project indicate that Volts are racking up
about 20% more e-mile than LEAFs, and in LA, 40% more.

Figure 3.

Turning it around: asset utilization

Another way to think about this effect is in terms of cost
effectiveness per e-mile. The comparison between vehicle capability and daily driving
highlights the “surplus” battery capacity in BEVs, on average. A ~100-mi
e-range appears to be necessary for BEVs to penetrate majority markets, but is
not, at this particular juncture, obviously more valuable from the perspective
of cleaning the air. Indeed, from the perspective of near-term e-mile
cost-effectiveness ($/e-mi), battery size is not an inherent “good.” Rather, it
is an asset that should be fully utilized each day in order to spread its costs
out over the maximum e-mile benefit it is capable of providing. Thus, even if a
vehicle averages 30 mi/day, if they only exceed 30 mi on 40% of days—as it
appears the 2009 National Transportation Household Survey indicates here [3]—on 60% of days the battery is
not fully utilized. Of course, BEVs do not have the luxury of being designed to
average needs. And the nominal cost-effectiveness of their batteries suffers as
a consequence.

This can be seen in Table 1, which assumes a $500-per-rated-kilowatt-hour,
across-the-board battery cost to illustrate the cost per e-mile of EPA-rated
electric range. In the first cost column, which examines vehicle capabilities,
all vehicles are roughly comparable, with most plug-in hybrids on the high end
of the spectrum. The second cost column, however, shows that costs per e-mile
of average daily driving vary quite dramatically, with capable BEVs suffering
for their “surplus” capacity.

Part of the confusion surrounding the debate on whether or
not PEV commercialization is going well or not [a matter I argue is more one of
Managing
EV Expectations] is the fact that media commentators often don’t properly
distinguish between the two very different products that are all-battery and
plug-in-hybrid EVs. California policy clearly does, however, to the significant
disadvantage of the vehicle type that is, at this particular moment in time,
probably pulling more than its weight of cleaning the air.

This is not necessarily to say that it shouldn’t. [We’ll
save that discussion for a future blog.] Or that the state shouldn’t stay on an
aggressive path towards large numbers of the truly zero-tailpipe-emission
vehicles that will be needed soon enough to meet the state’s daunting
challenges. Personally, I’d like to see all-battery EVs succeed; at one point
before moving to LA, I was on the waiting list for two different models. Further,
I’m used to imagining the long game, having previously criticized incremental
approaches by saying “a chasm can’t be crossed in two jumps,” and having worked
for what some would call a “controversial” and “bleeding edge” visionary.

However, as I expressed in The
Path of Least Resistance: An Introduction, I believe there is still an underlying
market dynamic that is both worth understanding and worth capitalizing on for
those truly interested in maximizing the penetration of all electric-fuel
vehicles and the benefits of their use. This is not about being incremental or myopic.
It is about a path complementary to the inspiring Tesla example and “beyond
oil” narrative—a path that may involve lower adoption costs (broadly defined)
and greater numbers of consumers. It is about getting going, truly going, with
PEVs. It’s about crossing the chasm to majority markets without letting a view
of the perfect be the enemy of the good that will come from getting more PEVs
on the road and cleaning the air.